Light-emitting diode (LED) devices have experienced rapid growth. LED devices have been referred to as a new generation light source, one capable of replacing incandescence lamps, fluorescent lamps and high-intensity discharge lamps. When compared to incandescence light sources, LED devices offer advantages such as reduced power consumption, longer lifetime, faster response speed, more compact size, lower maintenance costs, and greater reliability. LED devices have thus found many applications, including backlighting for displays, automotive lighting, general lighting, and flash for mobile cameras.
Thermal management for LED devices, especially for high bright LED devices (HBLEDs) is important to these LED devices' performance and lifetime. Thermal management may be implemented by techniques of enhancing heat dissipation and reducing heat production. To enhance heat dissipation, developments have been made in areas such as heat sink, printed circuit board (PCB) as well as LED packaging. To minimize heat generated by an LED device's immediate surroundings, techniques such as separating LED drive circuitry from an LED board have been implemented. The total power input for an LED device is the product of the forward AC voltage and the forward current of the LED device. A portion of the total power is the power to an LED device, which is a sum of the light generated by the LED device and the heat dissipated by the LED device. To minimize heat generated by an LED device, approaches such as using a constant current regulator have been explored. However, conventional techniques of protecting LED devices at high temperature operation have not been satisfactory in all respects. For example, detecting LED temperature accurately brings challenges in thermal management. Therefore, improved techniques of protecting LED device at high temperature operations continue to be sought. Input power is converted to light and heat. LED and phosphor efficiency for converting power to light goes down when they are hot. When efficiency goes down, more of the input power goes to heat, which makes the LED hotter. At high temperatures, the LED is damaged.